Integrin receptors are important for regulating both lymphocyte recirculation and recruitment to sites of inflammation (Carlos, T. M. and Harlan, J. M., Blood, 84:2068-2101 (1994)). The human α4β7 integrin has several ligands, one of which is the mucosal vascular addressin MAdCAM-1 (Berlin, C., et al., Cell 74:185-195 (1993); Erle, D. J., et al., J. Immunol. 153:517-528 (1994)) expressed on high endothelial venules in mesenteric lymph nodes and Peyer's patches (Streeter, P. R., et al., Nature 331:41-46 (1988)). As such, the α4β7 integrin acts as a homing receptor that mediates lymphocyte migration to intestinal mucosal lymphoid tissue (Schweighoffer, T., et al., J. Immunol. 151:717-729 (1993)). In addition, the α4β7 integrin interacts with fibronectin and vascular cell adhesion molecule-1 (VCAM-1).
Inflammatory bowel disease (IBD), such as ulcerative colitis and Crohn's disease, for example, can be a debilitating and progressive disease involving inflammation of the gastrointestinal tract. Affecting an estimated two million people in the United States alone, symptoms include abdominal pain, cramping, diarrhea and rectal bleeding. IBD treatments have included anti-inflammatory drugs (such as, corticosteroids and sulfasalazine), immunosuppressive drugs (such as, 6-mercaptopurine, cyclosporine and azathioprine) and surgery (such as, colectomy). Podolsky, New Engl. J. Med., 325:928-937 (1991) and Podolsky, New Engl. J. Med., 325:1008-1016 (1991).
Antibodies against human α4β7 integrin, such as murine monoclonal antibody (mAb Act-1), interfere with α4β7 integrin binding to mucosal addressin cell adhesion molecule-1 (MAdCAM-1) present on high endothelial venules in mucosal lymph nodes. Act-1 was originally isolated by Lazarovits, A. I., et al., J. Immunol. 133:1857-1862 (1984), from mice immunized with human tetanus toxoid-specific T lymphocytes and was reported to be a mouse IgG1/κ antibody. More recent analysis of the antibody by Schweighoffer, T., et al., J. Immunol. 151:717-729 (1993) demonstrated that it can bind to a subset of human memory CD4+ T lymphocytes which selectively express the α4β7 integrin. However, a serious problem with using murine antibodies for therapeutic applications in humans is that they are highly immunogenic in humans and quickly induce a human anti-murine antibody response (HAMA), which reduces the efficacy of the mouse antibody in patients and can prevent continued administration. The HAMA response results in rapid clearance of the mouse antibody, severely limiting any therapeutic benefit.
Thus, a need exists for improved therapeutic approaches to inflammatory bowel diseases.